I use photobucket.comĀ* it's free and they give you lots of space.
What is the best site to use for hosting pictures to use as links here?
To be honest with you if you're willing to part with a tiny bit of cash the BEST solution is your own webhost.
For example I have a couple of domains I own and put them on a webserver that costs me well under $10/month and allows me FAR more versatility and space than photobucket ever would.
Currently I have 100GB of webspace and 1TB of transfer alloted to me each month so even if I wanted to post full resolution images for download on a very busy forum it would be no problem.
Look into it it's worth it. a domain name can be had cheaply I personally used godaddy.com but there are others.
and as far as webhosts there are hundreds some better than others. Right now I'm migrating all my stuff away from www.ixwebhosting.com
because the 1and1 is far more stable and overall a better value.